Instructables user DIYHacksAndHowTo hacked the wireless doorbell by removing the original speaker from the doorbell, striping the insulation from the wires that ran to that speaker, and wiring the recording module to both the doorbell circuit board and a 9V battery. To record a tone, hold the microphone of the recording module near your computer speakers and press the record button on the module—this will give you up to 20 seconds of recorded audio. Whenever someone presses the doorbell it will trigger the playback.

This seems like a fun hack to try and if it doesn't work out you can always go with the commercial product; the Swann Wireless DJ Doorbell uses an SD card and easier to use but will also cost $50.